The present invention relates to a nozzle for fastening a material layer to a sub-structure, comprising a plate and a hollow shaft integrally formed thereon for receiving a fastening screw, a stepped hole being provided in the hollow shaft, the stepped hole comprising at least two steps between at least three regions, the hollow shaft being formed so as to taper conically at least in part on an outer surface, the hollow shaft being provided with radially expandable elements and the expandable elements being formed as axial grooves on the outside in the conically tapering part of the hollow shaft.
The present invention also relates to a fastening element for fastening a material layer to a sub-structure, wherein the fastening element is in two parts and comprises the nozzle according to the invention and a fastening screw.
One problem, which is often encountered in conjunction with building insulation, consists in fixing a material layer, for example insulating material and roofing membranes, to a sub-structure. In order to make it as easy as possible to mount an insulating material and a roofing membrane and to prevent any damage to the insulating material and/or the roofing membrane during mounting, fastening elements are usually used which comprise a nozzle and a screw which is adapted to the nozzle. Fastening elements and nozzles of this type are known from DE 296 18 959 U1, EP 0 600 284 A1 and EP 1 117 882 B1, for example.
E 35 00 084 A1 describes a fastening element comprising a plate and a short, integrally formed shaft. The shaft, which is designed to receive a fastening screw, comprises a stepped hole comprising a shoulder, which acts as a stop for the fastening screw in the mounted stated, and lips comprising sloping upper surfaces. In this way, a stepped holed having two steps is produced. Furthermore, longitudinal slots in the lower region of the shaft are also described, by means of which movable lips are provided on the lower shaft end which can be spread apart in a resilient manner when the fastening screw penetrates the shaft.
DE 10 2010 048 537 A1 describes a nozzle comprising a plate and a hollow shaft integrally formed thereon for receiving a fastening screw, a stepped hole being arranged in the hollow shaft, which hole has a total of four different radii. Furthermore, a length compensation element in the region of the shaft is described.
US 2012/0017529 A1 describes a nozzle comprising a plate and a hollow shaft integrally formed thereon, in which a fastening screw is received during mounting in order to attach a water impermeable membrane 114 and insulation 112 to a substructure 116, as shown in FIG. 13 of the present application. Lips which can flexibly bend outwards and are separated from one another by grooves are arranged on the lower end of the shaft. Furthermore, projecting ribs are arranged inside the hollow shaft, which allow the nozzle to be used reliably together with fastening screws of different thicknesses.
DE 36 06 321 A1 describes an insulating-board dowel comprising a plate and a hollow shaft integrally formed thereon, which comprises radially projecting ribs on the inside and outside thereof, by means of which drilled-hole tolerances are compensated.
A drawback of some of the known fastening elements is in particular the need to use different screws which are adapted to the present sub-structure or to the weight of the insulating materials used. Therefore, a large number of different nozzles which are adapted to the screws and the insulating materials also have to be provided. Overall, a large number of different nozzles and fastening elements thus have to be produced and supplied in order for a sufficiently secure fastening to always be possible.